Steam turbines include static nozzle (or “airfoil”) segments that direct flow of a working fluid into turbine buckets connected to a rotating rotor. A complete assembly of nozzle segments is commonly referred to as a diaphragm stage of the steam turbine. One method of constructing the diaphragm stage is to weld (or alternatively, braze) a plurality of single airfoils with integrated sidewalls (“static nozzle blades”, or “singlets”) to inner and outer rings. Each of these singlets have interfaces to which adjacent singlets are welded or brazed (in the inner and outer ring). These interfaces include an axial leading edge section (or “pressure-side” section) oriented parallel to the steam turbine's axis, and an angled trailing edge section (or “suction-side” section). While some prior singlet designs included angled interface sections allows for a tight fit between individual segments, the angled interfaces make removal and repair of individual segments nearly impossible.
More recent nozzle segments have incorporated arcuate sidewalls which permit removal of individual static nozzle segments from the ring without requiring removal of adjacent nozzle segments. However, these arcuate designs are not compatible with existing angled singlet sections, and as such, have been limited in use to new machinery manufactured with an entire section of nozzles having angled faces.